This invention relates to a manufacturing process of a fuel delivery rail assembly for an automotive internal combustion engine. This kind of assembly delivers fuel supplied from a pressurizing fuel pump toward intake passages or chambers via associated fuel injectors. The assembly is used to simplify installation of the fuel injectors and fuel supply passages on the engine.
There are two types of fuel delivery rail assemblies. One is a so-called top feed type and the other is a bottom flow type. The bottom flow type has several advantages including that the fuel is relatively free from vaporization since fuel passes through the center of the socket. Further, the height of installation becomes relatively small.
The process of the invention is applied to an offset-type rail assembly in which there are offset distances between an axial centerline of an elongated conduit and those of tubular sockets for receiving fuel injectors.
A typical construction of an offset-type rail assembly is disclosed in Japanese Utility Model Public Disclosure No. 14464/1990 entitled "Fuel Injection Apparatus for an Internal Combustion Engine". In this assembly, four sockets and an elongated conduit are formed into an integral unit through a casting process. These sockets and the conduit are arranged in an offset manner such that there are offset distances between the axial centerline of the conduit and those of the sockets.
These offset distances are provided so as to cause vortex flow or circulation flow within the socket in order to enhance efficiency of fuel injection into the engine cylinder.
If the offset is relatively large, arcuate edges should be formed in the conduit for receiving sockets. These arcuate edges have been made through machining work utilizing an end mill or similar tools. Then, TIG welding or Magne-TIG welding is applied to connect the sockets to the conduit.
However, there are many drawbacks in this machining work. For example, in addition to the time-consuming machining work, further time-consuming deburring work is needed to eliminate rugged burs. As a result, it takes a relatively long time to finish the arcuate edges.